1. Field of the Invention
The present invention relates to a dynamoelectric rotor for an automotive alternator, etc., and particularly relates to a lead construction for an output wire of a field coil.
2. Description of the Related Art
Conventional automotive alternator rotors include: a pair of field cores that are fixed to a rotating shaft; a field coil that is held between the pair of field cores; an annular body that is made of an insulating resin that is fixed integrally to the rotating shaft with the field cores and that has a flange portion that projects radially on an end portion near the field cores; and a pair of slip rings that are fixed to an outer portion of the annular body. A pair of leads for supplying current to the field coil are led out from positions on the field core that are on opposite sides of the rotating shaft and are connected to respective terminals of the slip rings (see Patent Literature 1, for example).
Patent Literature 1: Japanese Utility Model Publication No. SHO 59-1401 (Gazette)
In conventional automotive alternator rotors, because the pair of leads are led out from positions on the field cores that are on opposite sides of the rotating shaft, the number of turns of coil is reduced by one turn in a first circumferential half of the field coil. Thus, magnetomotive force of the field coil, which is expressed in ampere-turns, differs in the first circumferential half and a remaining second half. In other words, magnetomotive force that acts on a first half of magnetic poles and magnetomotive force that acts on a remaining second half of the magnetic poles differ from each other. As a result, one problem with conventional automotive alternators has been that the rotor is operated in a magnetically unbalanced state, generating magnetic noise. Moreover, because the frequency of the magnetic noise rises as the number of poles is increased, the magnetic noise becomes irritating.